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Copolymerization of ethylene and norbornene using cyclopentadienylzirconium trichloride activated by isobutyl-modified methylaluminoxane Part A Polymer chemistry

Nishizawa, Osamu, Misaka, Hideki, Sakai, Ryosuke, Kakuchi, Toyoji, Satoh, Toshifumi
Journal of polymer science 2008 v.46 no.22 pp. 7411-7418
aluminum, carbon, catalysts, composite polymers, ethylene, molecular weight, nuclear magnetic resonance spectroscopy, polymerization, stable isotopes, temperature, toluene, zirconium
The copolymerization of ethylene (E) and norbornene (NB) was investigated using the commercially available and inexpensive catalyst system, cyclopentadienylzirconium trichloride (CpZrCl₃)/isobutyl-modified methylaluminoxane (MMAO), at a moderate polymerization temperature in toluene. For the CpZrCl₃ catalyst system activated by aluminoxane with a 40 mol % methyl group and a 60 mol % isobutyl group (MMAO), the quantities of the charged NB and the polymerization temperature significantly affected the molecular weights, polydispersities, and NB contents of the obtained copolymers and the copolymerization activities in all the experiments. As the charged NB increased and thereby the NB/E molar ratio increased, the NB content in the copolymer increased and reached a maximum value of 71 mol %. The CpZrCl₃/MMAO ([Al]/[Zr] = 1000) catalyst system with the [NB] of 2.77 mol L⁻¹ and ethylene of 0.70 MPa at 50 °C showed the highest activity of 1690 kg molZr ⁻¹ h⁻¹ and molecular weight of 21,100 g mol⁻¹. The ¹³C NMR analysis showed that the CpZrCl₃/MMAO catalyst system produced the E-NB random copolymer with a number of NB homosequences such as the NN dyad and NNN triad.